An outboard motor is a propulsion machine for propelling a boat by rotating a propeller mounted to a stern by the drive of an engine. The engine is covered by a cover for watertightness.
In order to prevent water from being mixed into an intake air to be taken into an engine, means for preventing water from entering through an air introduction portion of a cover and means for separating water from air have been devised. For example, a barrier for preventing ingress of water is provided midway along an intake passage, or an intake passage is provided such that only an intake air flows up to prevent entering of water, or an intake passage is bent to deflect the ingress direction of water so as to separate water from air.
When a required amount of intake air of an engine is larger, an intake passage needs a correspondingly larger opening area. The presence of the intake passage in the engine compartment, however, greatly affects the external dimensions of an engine cover.
An outboard motor with an intake passage provided along the rear and the side of an engine in an engine cover as an intake passage for introducing air into an engine compartment of the outboard motor is disclosed, for example, in Japanese Patent Laid-Open Publication No. HEI-4-166496.
In this outboard motor, an intake chamber communicating with an intake section of the engine is provided in such a manner as to vertically extend on one side within the engine compartment. In the engine compartment, an intake duct for introducing air from an air intake provided in the engine cover on the other side of the engine compartment into the intake chamber is provided in such a manner as to go around the rear of the engine.
The intake passage is configured with a single intake duct, thus having a large vertical section area or horizontal section area. The disposition of the passage of a large section area along the rear and the side of the engine results in a large contour of the engine cover for avoidance of its interference with the engine and auxiliary machinery around the engine. That is, the fore-and-aft dimension of the engine cover is increased, and also the lateral dimension of the engine cover is increased. Thus, the contour of an engine cover portion constituting an upper half of the outboard motor is enlarged in fore-and-aft and transverse directions.
When the outboard motor with the contour of the engine cover enlarged fore and aft, which is mounted tiltable to the stern of a hull, is rotated upward about a tilt shaft, the path of the outermost portion expands radially about the tilt shaft, being unsuitable for the hull. Consequently, when choosing an outboard motor, the range of choices is narrowed.
It is thus desired to ensure a necessary and sufficient amount of air intake of an engine without greatly affecting the external dimensions of an outboard motor.